No abstract

There is no evidence from these results to support the involvement of adenosine to any major extent in preconditioning induced protection of postischaemic contractile function in the isolated rat heart.

Serum total antioxidant activity (TAA), albumin and uric acid were measured on admission, and for the next 2 days in 56 patients suffering myocardial infarction, 20 of whom received streptokinase. The ‘antioxidant gap’, the difference between the serum TAA and the sum of the serum albumin and uric acid activity, was calculated. No significant changes in serum total antioxidant activity were observed in either group of patients between admission, day 1 and day 2. However, a decline in the ‘antioxidant gap’ after myocardial infarction was associated with a significantly higher mortality.

The kinetic constants and sodium independence of amino acid uptake by the basolateral face (blood side) of the isolated perfused choroid plexus of the sheep were investigated. Uptake of 3H-labeled L-alanine, glycine, L-glutamine, L-leucine, L-glutamate, and L-lysine was not significantly inhibited when the sodium level of the perfusate was lowered to less than 6 mM. The cerebrospinal fluid (CSF) secretion rate was, however, reduced by 65.6%. The Michaelis constants for L-serine, glycine, L-phenylalanine, L-glutamate, and L-arginine were measured and varied between 25.4 microM for L-arginine and 2.6 microM for L-glutamate. The Vmax for the amino acids varied by about the same range as Km, with L-serine having the highest Vmax of 28.8 nmol.min-1.g-1, and L-phenylalanine having the lowest at 4.6 nmol.min-1.g-1. At normal plasma concentrations of 30-155 microM for individual amino acids, the carriers for glycine, L-phenylalanine, and L-glutamate would be almost fully saturated (greater than 90%), while those for L-serine and L-arginine would be greater than 60% saturated. This restricted uptake of amino acids by the basolateral face of the choroid plexus, coupled to clearance of these substances out of the CSF (5), could account for the low levels in the CSF compared with that in the plasma.